In an ALD method that is of one of thin-film forming techniques, two kinds of gases composed mostly of elements constituting a film to be formed are alternately supplied onto a deposition target substrate, and a thin film is repeatedly formed plural times in units of atomic layers on the substrate, thereby forming the film having a desired thickness. For example, a source gas containing Si and an oxidation gas containing O are used when a SiO2 film is formed on the substrate. A nitridation gas is used instead of the oxidation gas when a nitride film is formed on the substrate.
So-called growth self-stopping action (self-limiting function) is utilized in the ALD method. That is, only a source gas component for one or several layers is adsorbed to a substrate surface while the source gas is supplied, but the excess source gas does not contribute to the growth.
When compared with a general CVD (Chemical Vapor Deposition) method, advantageously the ALD method has both high step coverage and film-thickness controllability. Therefore, the ALD method is expected to be practically applied to the formation of a capacitor for a memory element or an insulating film called “high-k gate.” Additionally, the insulating film can be formed at a temperature of 300° C. to 400° C. in the ALD method. Then the ALD method is also expected to be applied to the formation of a gate insulating film for a thin-film transistor in a display device such as a liquid crystal display in which a glass substrate is used.
For example, in a deposition apparatus described in Patent Document 1, the source gas reacts in a reaction chamber of one reaction container to form the thin film on the substrate, and a volume of the reaction chamber of the reaction container is variable. A heater, on which the substrate is placed, moves up vertically to abut on a stopper, thereby reducing the volume of the reaction chamber.